Thanks to the excellent work of the iPhone Dev Team and the porting work of Jay Freeman as well as the authors of 3Proxy, it is now possible to “tether” your iPhone 3G and use its Internet connection on your laptop.

Warning - Tethering your iPhone is against the iPhone data plan terms. AT&T could slap you with huge fees if you overuse this. I recommend only using it during emergencies.

Here’s the basic rundown:
- Jailbreak your iPhone 3G
- Install 3Proxy and Terminal
- Create an ad-hoc Wi-fi network using your laptop
- Join the network with your iPhone
- Find the iPhone’s IP address
- Open Terminal and run the proxy program
- Open Safari on your iPhone and open a web page
- Configure your browser to use the proxy

I will be using a Mac and Firefox to demonstrate, but the principles carry over to other platforms…